I have a Compose key binding in https://github.com/kragen/xcompose which maps Compose Space Minus to "—" with two thin spaces on each side of it, because I prefer the spaces. But HN rewrites the thin spaces to regular spaces, so on HN I just use "—" without the spaces, the way ChatGPT does, which is Compose Minus Minus Minus, and is in the standard Compose key bindings (if you map your keyboard to have a Compose key at all).
Same. I feel like I've been using "--" in my online writing for decades now. Take that, LLMs; I used it before it was cool... er... before it was a weak signal that a piece of text was written by an LLM.
In LaTeX (and probably smartypants which is another of those bare pre-unicode ASCII to fancy text converters that can get stacked into markdown--but I can't remember if dash handling specifically is in there), "--" is en-dash and "---" is em-dash. The single "-" gives a hypen which is handled differently than an en-dash in typesetting.
So... that's just to say that people who are exposed to the sorts of can't-unsee-it-now typesetting OCD that LaTeX and various popular extension packages within that ecosystem exposes can learn to write write "--" as en-dash.
It's sort of like being unable to return to the blissful state of not being hyperaware that Ariel and Helvetica are different.